Broadcom driver for OpenBSD was developed in spite of fierce opposition by Broadcom which publicly stated on many occasions that they want their customers to run only Windows. NetBSD has the driver for Broadcom devices. I think though that it is only OpenBSD driver ported to NetBSD so should not support more devices.
There is FreeBSD port of the same driver circulated among developers but nobody have committed it yet to kernel. Most Broadcom devices also require firmware.

You only chance is to try ndis utility in FreeBSD and generate the FreeBSD driver form the Windows driver (YMMW). Other than that I would ditch Broadcom since they obviously do not want us as customers.

We also have a mailing lists (misc AT openbsd comes to mind) for general
questions but before you post something there look the mailing list archives
as most of the questions have been answered already.

OpenBSD is one of the best documented Operating Systems and projects around. OpenBSD is also probably the simplest and most logical version of Unix around. It is not for everyone and for everything though.

Community is very friendly and helpful but OpenBSD is not about hand holding like many other projects.